This invention concerns circuits for interfacing a central unit and a plurality of remote terminals; it concerns, more particularly, interface circuits for use in telephone systems.
Data processing installations have been increasingly developed which include terminals such as cathode ray tube display devices, teleprinters, telephone sets. etc. connected to central units. When the connection is carried out through wires the use of interface circuits between the line and the central unit is necessary to ensure safety. These circuits include transformers the presence of which raises serious problems in the electronics systems wherein it is desirable to reduce both cumbersomeness and cost.
Many solutions have been proposed to solve these problems. Most of them tend to replace the transformer by an equivalent active circuit and to make use of opto-electronic couplers to ensure the galvanic isolation characteristic of the transformer. Unfortunately, the present state of the technology in this field cannot secure the characteristics of these couplers as to their stability in the course of time, thereby reducing their effectiveness considerably.
The object of this invention is to provide for an interface circuit of small size having stable galvanic isolation.
The foregoing and other features, advantages and objectives of the present invention may be more fully understood and appreciated by considering the following detailed description.